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The use of nanoparticles in medicine, nanomedicine, is very important to diagnose and treat diseases; among the various metallic nanoparticles, silver nanoparticles (AgNPs) are very popular due to their physical, chemical, and biological properties, encompassing a range of activities such as antiviral, antifungal, anti-inflammatory, and anticancer activities. In this study, the synthesis of AgNPs was conducted by the use of a nontoxic, ecofriendly method. Green tea (GT) leaf extract was used as a reducing agent to convert silver ions into free AgNPs. The UV-vis spectrum showed a peak at 410 nm, confirming the presence of AgNPs. A Fourier-transform infrared (FTIR) analysis of the GT extract and GT AgNPs display spectra that is identical to those of polyphenols, polysaccharides, and proteins. All the vibrational peaks in the GT extract spectrum were shifted in the AgNP spectrum, becoming narrower after the encapsulation of nanoparticles. The scanning electron microscopy (SEM) images confirm the presence of AgNPs with different sizes, ranging from 15 to 33 nm. Furthermore, the antibacterial activity of the synthesized AgNPs in three different concentrations (10, 20, and 50 mg ml-1) showed appreciable inhibition of bacterial growth against Staphylococcus aureus and Klebsiella sp. From the above findings, we can recommend the use of AgNPs from GT leaf extracts as an antimicrobial agent to treat chronic infections.
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[This corrects the article DOI: 10.1039/D1NA00509J.].
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BackgroundRapid and accurate testing for SARS-CoV-2 is an essential tool in the medical and public health response to the COVID-19 pandemic. An ideal test for COVID-19 would combine the sensitivity of laboratory-based PCR combined with the speed and ease of use of point-of-care (POC) or home-based rapid antigen testing. MethodsTo evaluate the performance of the Diagnostic Analyzer for Selective Hybridization (DASH) SARS-CoV-2 POC PCR (sample insertion to result time of 16 minutes), we conducted a cross-sectional study of adults with and without symptoms of COVID-19 at four clinical sites. We collected two bilateral anterior nasal swabs from each participant and information on COVID-19 symptoms, vaccination, and exposure. One swab was tested with the DASH SARS-CoV-2 POC PCR and the second in a central laboratory using Cepheid Xpert Xpress SARS-CoV-2 PCR. We assessed test concordance and calculated sensitivity, specificity, negative and positive predictive values using Xpert as the "gold standard." ResultsWe enrolled 315 and analyzed 313 participants with median age 42 years; 65% were female, 62% symptomatic, 75% had received [≥]2 doses of mRNA COVID-19 vaccine, and 16% currently COVID-19 positive. There were concordant results for 307 tests indicating an overall agreement for DASH of 0.98 [95% CI 0.96, 0.99] compared to Xpert. DASH performed at 0.96 [95% CI 0.86, 1.00] sensitivity and 0.98 [95% CI 0.96, 1.00] specificity, with a positive predictive value of 0.85 [95% CI 0.73, 0.96] and negative predictive value of 0.996 [95% CI 0.99, 1.00]. The six discordant tests between DASH and Xpert all had high Ct values (>30) on the respective positive assay. DASH and Xpert Ct values were highly correlated (R=0.89 [95% CI 0.81, 0.94]). ConclusionsDASH POC SARS-CoV-2 PCR was accurate, easy to use, and provided fast results in real-life clinical settings with an overall performance similar to an EUA-approved laboratory-based PCR. Its compact design and ease of use are optimal for a variety of healthcare, and potentially community settings, including areas with lack of access to central laboratory-based PCR testing. SummaryDASH is an accurate, easy to use, and fast point-of-care test with applications for diagnosis and screening of SARS-CoV-2 infection.
